Call-xistribtjtina  system



R. L. QUASS.

CALL DISTRIBUTING SYSTEM.

APPLICATION FILED OCT. 8. 1917.

5 SHEETS SHEET l. 4

Patented July 1,1919,

R. L. QUASS. CALL DISTRIBUTING SYSTEM.

APPLICATION FILED OCT. 8. I917.

Patented July 1, 1919.

5 SHEETS-SHEET 2- yew far fia/p/ A. 04/4755.

R. L. QUASS. CALL DISTRIBUTING SYSTEIVIfQ' APPLICATION FILED OCT. 8'I917.

mmwfimm Patented July 1, 1919.

5 SHEETS-SHEET 3.

Fez/ ab L. Quass.

H. L QUASS. CALL DISTRIBUTING SYSTEM.

APPLICATION FILED OCT. 8. I911.

Lwg m v Patented July 1, 1919.

5 SHEETS-SHEET 4.

I R. L QUASS. CALL DISTRIBUTING SYSTEM.

APPLICATION FILED OCT. 3. I917.

IPfl'IGllIJGdI July I, 1919. 5 SHEETS-SHEET 5 'mwwm UNITED STATES PATENoFFIo [men L. QUABS, or mwrnonnn, new mnsnm ssszenon TO wesem snnornrc Illll lid

0mm, INCOBPOBATED, OIN EW YORK, N. Y.,"" A CORPORATION OF NEW YORK.

To all whom, it may concern I 5136 it. known that '1, Rem x; L. Qrmsahcitizen of, the United States,v residing at tributih Systems, of whichthe followin is a full, c ear, concise, and exact descri tion.

This invention relates to telephone ca dis-- tribnting systems of thetype in whichthe calls orginated by the lines of the exchange areautomaticall distributed to o craters positions at w ic connection witht e called subscribersulines is completed. The invention has primaril todo with the provision of means for sa eguarding such a system againstfailures of operation which mi ht result from careless manipulation of te, ap paratus on the part of the operators, or which might arise fromthe improper operation of the apparatus itself, the ob ect beingto-improve and render more eflicient and reliable the operation of thesystem.

Generally stated, the system of the preferred embodiment of theinvention herein disclosed provides a plurality of operators positionseach equipped with a number of plug-terminated connecting circuits forcompletmg connection with called subscribers lines, The connectionbetween these connecting-circuits and the calling subscribers lines iseffected throu h the medium of a number of finder circuits, each ofwhich has an automatic switch at one end for finding and connectin withany subscribers line that may be calli at the other end for selecting anavailable operators position and then connecting with an idle connectingcircuit at that position. The connecting circuit to which the connectionis extended terminates in a plug, and the o erator completes connectionwith the called subscribers line by inserting the plug into thespring-jack of that line.

lln the selection of an .operators position by the finder circuitcertain devices are operated that render the position inaccessible toother incoming calls, and the position remains inaccessible untilcertain other apparatus operates to restore its accessibility.Similarly, the selection of an idle connecting circuit by the incomingcall renders that connecting circuit inaccessible to other cells untilthe accessibility of the circuit is restored by taking down theconnection.

f Specification of Letter! Patent. Application filed October a, 1917.semi Ho. issue.

ng,-and an automatic switch been extended.

- ioamnisrnrsvmo svsrun.

Patented July 1 1919.

The idle oraccessible condition of a concircuit, in the potentialbattery with the test conductor associated with the connecting circuit.One

of the ob e'ctS of the present invention is so to organlze the systemthat when, by the nectigg present system, is indlca by'the connectlonofrelatively high accidental grounding of one of the test conductofeor-otherwise, an abnormal electrical cond1t1on o: E the testing circuitsof an operators posltionis created, that position is I automatlcallymade inaccessible to incoming calls, while at the, same time the abilityof the operator to supervise existing connections is not interferedwith. Another object of the invention is to provide means for signalingtheoperator of the selection of her osition' the instant the selectionoccurs, and or withdrawing the signal after a predetermined timeinterval, or at the instant the connecting circuit is seized if theseizure takes place before the ex iration of that timeinterval. Anotherob ect of the invention is to provide means for preventing holding theoperators position unselectable for more than a predetermined intervalin the event of an abnormal operation of the apparatus which controls te connection of the operators telephone with a connecting circuit whenthe operator listens in on that circuit. Another object of the inventionis to prevent an unintended release of the callingillme from theconnecting circuit to which it as been extended in case the operatorhappens to insert the calling plug into the spring-'jackof the calledsubscribers'line in such a way as momentarilyto break the connection asthe plu moves into the spring jack. Another obJect 0f the invention isto give an operator a characteristic signal or indication when sheinserts into the springjack of a line the calling plug of a connectingcircuit to which a calling line has not of the system.

' mm the relationshi between them, Fig. 3 shows two cord s ector'switchesof one frame with their associated selection controllingapparatus and circuits, together with similar apparatus and circuits forthe cord selector switches (not shown) of another frame; and Figs. 4 and5 show the position circuit may be connected. The figures takentogether, and arranged side by side in the or er indicated by the linesthat extend to the margins of the sheets, illustrate as much of acomplete organization as is necessary to gain an understanding of theconstruction and mode of operation of the system.

The telephone lines are indicated in each of the two groups shown inFig. 1, it being understood that each group may comprise a large numberofsuch lines. The practice is to give the finder swltch brushes accessto the terminals of five hundred "lines, these lines being arranged inten groups of fifty lines each. Each of the lines has associated with itat the central ofiice a line relay 12 and a cut-off relay 11. Each lineis also provided with one or more spring-jacks 14 by means of whichconnection may be made with the line when it is a called line. The linesrepresented as calling lines in Fig. 1 and the line shown as a calledline in Fig. 5 may be lines of the same sort, similarly equipped andlocated at the same exchange; or the lines may be located at differentoffices. In the present instance, the called line shown in Fig. '5 isindicated as being provided with connections by means of which it mayhave control over finder'switch mechanism 1n the mannerillustrated inconnection with the lines of Fig. 1, Each group of lines, LG and LG, hasassociated with it certain group apparatus consisting of two relays 19and 24, a common protective relay 250, and a timing sequence switch 100.There is also provided apparatus common to all of the line groups,comprising the relays 22, 23 and 33.

The groups of lines have access to groups of connecting circuits throughthe medium of finder circuits F, F, F, which terminate upon the brushesof pairs of finder switches of which twosets, LF and CS and LF and CS,are shown. Each of the groups of connecting circuits is associated witha particular operators position, of which the apparatus of one is shownat O and the apparatus of the other is partially shown at 0.. In theparticular svstem illustrated, it is the practice to provide eachoperators position with twenty-five connecting circuits extending tomultiple groups of terminals upon the cord selector switches, and togive the merely dia brushes of each cord selector switch access to theterminals of twenty such g"oups of connecting circuits".- But one of theconnecting circuits is shown complete, the other connecting circuits inthe associated group and in the other groups being similarly organizedand connected. Multiple connections of'the connecting circuit with theterminals of the cord selector switches are shown in the case of theconnecting circuit that is indicated and the one that is completelyillustrated; and in like manner multiple connections of the tele honeline with the terminals'of the line fin er switches are shown in thecase of the lines that extend from the two stations shown. The multipleconnections that exist between corresponding sets of switch terminalsand the other connecting circuits and telephone lines are omitted toavoid confusing the drawing. A number of groups of cord selectorswitches like the group illustrated in Fig. 3 may have access to thesame groups of connecting circuits and their corresponding operatorspositions. This is indicated in Fig. 3. Each of the oups of cordselector switches has associated with it certain selection controllingapparatus, that associated with the cord selector switches shown in Fig.3 appearing under the caption Frame 2, and that associated with the cordselector switches of the other group that is not shown appearing underthe caption Frame 1. The selection controlling apparatus for each frameor group of cord sclcctor switches comprises a set of relays 77 93, and94 for each operators groups, CG, CG, to which the cord selector hasaccess, and a group of relays 54, 55, 61 and 63 common to all of thefirst mentioned groups.

As the line finder switches LF and LF, and the cord selector switches CSand CS in themselves are not novel, they are shown ammatically. Theseswitches be substantlally like the switch illustrated and described inthe patent to James L. Mc- Quarrie, No. 1,177,044, issued March 28,1916. The line finder and cord selector switches are alike in allsubstantial respects.

Each comprises a longitudinally movable shaft 1 carrying as many sets ofbrushes 2 as there are groups of stationary terminals to be engaged. Tomove the shaft up, an extension at the lower end of the shaft is broughtinto engagement with the con- 120 stantly rotating power member 3 bymeans of an idler Wheel operated by the up-drive magnet 32; and to movethe shaft down, tho. extension is brought into engagement with the powermember 4 by means of an idler wheel operated by the down-drive magnet62.

Normally the brushes of .each of the sets 2 are held apart, so as toclear the associated terminals, by means of a separating 130 eeann camlocated between the innermost brushes lit of the set. The com 5 isrotatably mounted, and when rotated in one direction, releases thebrushes and permits'them to engage the associated terminals. Thetripping or releasing of the brushes is controlled ya number oftrip-magnets 16, 17. Each of these when energ1zed rotates an associatedtrip rod 6 that extends transversely. to the sw1tch shafts 1 and carriesas man tripping yokes l as there are finder swltc we in the group. Thetrip rod,-in rotatmg, brings all oi its tripping yolres 7' into positionto .o

crate the rush controllin came 5 of t e corresponding sets of brushes onall oi the switches, so that whichever ot the finder switches is causedto move uphas that set oi brushes tripped that corresponds with theparticular trip magnet 16, 17, that is at the time energized, When thefinder switch that has been in use is returned to its. nor mal position,any of the associated controlling cams 5 that has been tripped isengaged and rotated in'a reverse direction to separate its switchsorings again and thusrender them inactive.

as :in the various stages oi the upwardnuove tit Roch oi the line finderand cord selector switches has associated with it a commutator whichcomprises a number ct stationary commutator segments and a set ofmovable brushes carried at the top oi the switch shalt land cofiiratingwith the stationary i 's commutator serves to u ment of the switchshaft. I a

For controlling thecircuits of the organization, there are employed anumber oil sequence switches which are shown at dliierent points and aredesignated 100, 9200,

300, e00 and 500, res ectively. Thesedse e 1suence switches'may e of thet c osed in Patent 1,127,808 issued'lie rua 0, 1915, to Reynolds andBaldwin. Rae consists of an electromagnetically controlled motor ordriving mechanism and'a number of associated switch cams. The switchcams associated with each of the sequence. switches 100 are designated101 to 103 inclusive; those associated with each of the sequenceswitches 200 are designated 201 to 223 inclusive; those associated witheach of the sequence switches 300 are designated 301 to 310inclusivegthose associated. with each of the sequence switches 400 aredesignated 401 to 416 inclusive, and those associated with each of thesequence switches 500 are designated 501 to 519, inclusive. To each ofthe contacts associated with the various sequence switch cams are aplied certain numerals. These numerals n the caseof the cams 101, 201,801, 401 and 501 indicate the only positions of the associated sequenceswitch in which these particular contacts are open; the numerals appliedto all of the other contacts of each sequence switch indicate the onlyositions of the particular associated switc in which the associated,contacts are closed.

The sequence switches 100 merely act as timing switches and have onlyone resting position. The resting positions of the other sequenceswitches, and the stages of operation with which these positions areassociated, are as follows:

' Sequence switch R00.

1. Normal. 1 2. Awaiting starting circuit.

3. Awaiting startin circuit release. A. Hunting calling 'ne.

0. Awaiting precedin finder circuit.

l. Awaiting operators selecting circuit. d. Releasing operator sselecting circuit. 0 Hunting cord circuit.

. Talking. Line finder at tell-tale. Cord selector at tell tale.

Line finder return.

. Cordselector return.

Sequence switch 300.

1. Awaiting a call. 4-. Position vacant. Position busy.

Sequence switch 400. 1. Normal. 7. Listening in.

. Listening out...

dogmat c switch Z5110. Normal.

. Awaiting listening they sequence switch. N I

@ Selective ringing operations.

13. Ringing called line. 16. Awaiting supervisory relay. 17. Talking.

. Themanner in which the system is organized will appear from thedescription of its operation which follows. It w1ll be assumed that thesubscriber at station A initiates a calL. When the tele hone receiver istaken from the switchhoo a circuit is closed that extends by way of bothwindings of the line relay 12 and both limbs of the telephone line, andis completed in the-contacts of the switchhook at the subscribersstation. The flow of current in this circuit energizes the line relay12, which in operating applies at its right-hand armature and contact, aground to the conductor 18. This causes current to How from batterythrough the winding of the relay 19, sequence switchcontact 103 (18% to1 conductor 18 and ground at the contacts of the operated line relay 12.The relay 19 attracts its armature and closes a circuit that extendsfrom battery through the right-hand winding of the associated relay 24,front contact of relay 19, back contact {of relay 22 and lower armatureand back contacts of relay 32 to ground. Relay 24 operates and closes atits left-hand front contact a circuit that extends from battery by wayof the winding of the associated group trip magnet 16 and the left-handwinding of the relay 24, in parallel, to the front contact of thatrelay, and thence by way of conductor 58, the winding of the relay 22,and the lower arms ature and back contact of therelay 23 to ground.

Current flowing in the circuit traced above operates the trip magnet 16of the group in which the calling line is located, locks up the relay 24of theassociated group and operates the relay 22 common to all of thegroups. The tri magnet 16 rotates its associated trip rod to bring allof the yokes into position to tri the corresponding set of brushes ofwhic ever of the line finder switches is started. The group relay 24breaks, at its left-hand back contact, thecircuit of the conductor 58 tothe corresponding relays 24 of the succeeding groups of the series.

The relay 24, at its right-hand front contact, also completes a circuitthat extends from battery through the motor magnet of the sequenceswitch 100, and contact 102 (18% to 1%) of that switch. In moving out ofposition 1, sequence switch 100 closes its contact 101 and opens itscontact 103. As contact 101 is closed in all positions exceptingposition 1 of the sequence switch, the switch is caused to make onecomplete rotation; and as contact 103 of the sequence switch is open inall positions excepting positions 18% to 1%, the conductor 18 is heldopen while the sequence switch is making its revolution and until itgets back to position 1. The time required by the sequence switch tomake one complete rotation is so regulated as to be greater than thatoccupied by the line finder switch in finding the terminals of anycalling line. The action, therefore, is such as to interrupt the groupconductor 18, and hold it open until after the line relay 12 of thecallin line has been released as a result of the line.

The relay 22, common to all the groups, in

zation of the associated relay 24 and ti ending of that operation of thecorrespondin trip magnet, the interruption of this con uctor insures theoperation of only one trip magnet and the tripping of only one set ofbrushes on a started line finder switch.

The common relay 22, when it operates, applies ground to the startingconductor 29 to start a finder switch huntin for the calling line. Thestarting con uctor 29 has branches extending to like sequence switchcams 206 of all of the finder circuits terminating upon the line findersthat have access to the callin line. But, for reasons which will hereinar be explained, the sequence switch 200 of only one of these findercircuits is standing in its 2 position. Assuming that this is thesequence switch of finder circuit F, when the relay 22 is actuated bythe calling line, as already described, a circuit is completed thatextends from battery through the left-hand winding of relay 30, sequenceswitch contacts 206 (2), conductor 29, front contact and armature ofstarting relay 22, lower armature and back contacts of relay 23 toground. The right-hand winding of relay 30 is at this time also included in parallel with the left-hand winding of the relay in theenergizing circuit, the parallel branch being from battery throughresistance coil 56, sequence switch contacts 217 (2 to 9) right-handwinding of relay 30, se uence switc contacts 220 (2) and (1 to 13thereafter joining the conductor that extends from the left-hand windingof relay 30, and to ground over the circuit already traced. The effectof this is to give the relay 30 the benefit of the energizing action ofboth windings.

As a result of the closure of the circuit traced above, the relay 30 isenergized and closes a circuit that causes the associated sequenceswitch 200 to move out of position 2. This circuit extends through themotor magnet of the sequence switch 200, sequence switch contact 202 (2)ri ht-hand front contact and armature of 're ay 30, sequence switchcontact 208 (2 to 7), conductor 79, commutator segment M of theassociated cord finder switch CS, and to ground by way of the brush thatis in engagement with this commutator segment. Relay 30, in attractingits armatures, also closes a locking circuit for itself that extendsfrom battery by way of the resistance coil 56, sequence switch contacts217 (2 to 9), the right-hand winding of the relay 30, sequence switchcontacts 216 (2 to 4) and (2 to 9), front contact and left-hand armatureof the relay 30, and armature and back contact of the relay 37 toground.

As a result of the closure of its motor magnet circuit in the right-handfront contact of the relay 30, the sequence switch 200 moves out ofposition 2 and comes to rest in position 3. In position 3 of the switch,a

circuit is closed that extends from battery by way of the up-drivemagnet 32 ofthe corresponding line finder switch LF, con-, ductor 59,sequence switch contact 207 (3 to a), front contact and ri ht-handarmature of relay 30, sequence switch contact 208 (2 to 7)., and toground by way of conductor 7 9 and the commutator segment M andassociated brush of the corresponding cord finder CS. The energizationof theupdrive magnet 32 starts the upward movement of the correspondingelevator rod with its associated sets of ushes. At the outset of the u'ward movement of the elevator rod, all the brush trip levers are movedpast the corresponding trip yokes. The only trip magnet that isenergized in this case is the magnet 16 which corresponds with the groupin which the callin line is cats and, consequently, the on y tri yoke inposition to engage a tri lever on t e elevator rod is the one w ichcontrols the brushes 10, 41, 42 and 43 that are adapted to engage theterminals of that particular roup of lines. This set of brushes,thereore, is released and made 0 erative, and the other sets are heldclear 0 theirassociated line terminals.

As soon as the set of brushes corres onding with the calling line istripple the group apparatus, by means of w 'ch the ines control thebrush trippin finder starting operations, may 6 returned toits normalcondition. The first step in this restoring operation is eflected by theclosure of a. circuit which is completed by way'of the K segment of theline finder commutator immediately after the brushes are tripped. Thiscircult extends from battery in parallel branches through the relays 23and 33 see Fig. 1), conductor 26, sequence switc contact 209 (2:1 to 3conductor 68, and to ground by way of t e K segment of the line findercommutator and its associated brush. The energization of the relay 23interrupts, at the lower back contact of that relay, the reviouslydescribed circuit that has up to t is time maintained the ener izationof the trip magnet 16, the group re ay 24 and the common starting relay22. Relay 23, at its upper front contact, closes a locking circuit foritself and the associated relay 33 that extends by way of conductor andthe se uence switch contacts 210 (2% to 1) of al of the finder circuitsin series, to ground at a point beyond the last switch of the series.

As has already been stated, normally there is only one of the findercircuits wit bit osition 2 awaiting the finder circuits are in positionto close their contacts 210. The locking circuit. for the relays 23 and33 is, therefore, held closed until another one of the finder circuitshas its sequence switch moved into position 2. This is accomplished byrelay 33, which, in operating, conductor 28 to move the sequence switchof another finder circuit out of position 1 and into position 2 andwhich also applies a ground to the conductor 27 to move the sequenceswitch of the appropriated finder circuit out of position 3.

Assuming that the sequence switch of finder circuit F is in position 1and that the sequence-switch of finder circuit F is in some positionbetween 4 and 17, that finder circuit being assumed to be in use, theoperation of the relay 33 completes the fo1- lowing circuit: frombattery, through the motor magnet and contact 203 (1) of the sequenceswitch of finder circuit F, conapplies a ground to tacts 211 (1) of thesame sequence switch,

contacts 211 (3 to 17 and (4 to 17) of the sequence switch 200 of findercircuit F contacts 211 (3 to 17) and (3 to 3%) of the sequence switch200 of finder circuit F, conductor 28, lower contact and armature of therelay 33 to ground. This causes the sequence switch of finder circuit Fto move into position 2. and 11118..

If by any chance the sequence switch of finder circuit F should'failtobe moved into the call-awaiting osition 2 when the relay 33 operates, itwill be moved into that position when the sequence switch of the appro-,

priated finder circuit F moves into position 5 at a slightly later stagein the operation. The circuit by which this result would, under thecircumstances, be accomplished extends from battery throu h the motormagnet and contact 203 (1 of the sequence switch of finder circuitcontacts 211 (1') of that sequence switch, sequence contacts 211 (3 to17 and (4-to 17) of finder circuit F (assume to be in use), and thenceby we of contacts 222 (5 to 1) of all of the fin er circuit sequenceswitches in series to ground. In other words, at any time that thefinder circuit sequence switches are all standing in position 1 or inosition 5 and beyond, a ground is applied y way of the 222 cams inseries that moves one of. the switches into osition 2, and thus lacesthe associated fin er'circuit in its cal -awaiting condition. Thesequence switch of finder circuit F is moved out of position 3 by theclosure of a circuit that extends from battery throu h the motor magnetand contacts 203 (3) o the sequence switch of that circuit, conductor 27and upper contact and armature of relay 33 to ound. As'soon as thesequence switch oE finder circuit F moves into position 2, it opens atits contact 210 the circuit by way of conductor 25 armatures.

which has been maintaining relays 23 and 33 energized and these relaysrelease them I ela 23, in releasing, reconnects to ground t e circuitwhich extends in branches 57 and 58 through its various sets of grouprelays, thus again giving the groups access to the starting circuit.

At this Stage of the operation of the system, the sequence switch of theappropriated line, the test relay 37 of the finder circuit is connectedwith local conductor 253 of that line. This local conductor has twobranches, one or the other of which is closed depending upon thecondition of the line relay 12 of the associated line. If the line relayis inert, as it is when the line is not calling, or when the line hasbeen connected with and its cut-ofif relay operated, the local conductor253 of the line is connected with ground by way of an identifying device252 and a relatively low potential battery. If

the line relay 12 is energized, as it is when the line is calling and isnot connected with, the local conductor 253 of the line is connectedwith ground by way of the righthand back contact and armature of theprotective relay 250 common to a group of lines,-

the energizing winding of this relay, and a relatively high potentialbattery 251. Therefore, as the elevator rises and the brush 43 engagesthe corresponding terminal 47 of each, of the lines of the group inwhich the calling line is located, a circuit is completed as each lineterminal is engaged that extends, either by way of the low potentialbattery, the device 252, and the left-hand back contact and armature ofrelay 12 to the local conductor 253 of the line; or by way of the highpotential battery, the winding of common relay 250, the right-handarmature and back contact of that relay and the left-hand front contactand armature of relay 12 to the local conductor 253; and thence by wayof line terminal 47 brush 43, conductor 51, finder sequence switchcontacts 204 (1 to 8) and (2% to 4), and winding of relay 37 to ground.

The relay 37 is so adjusted that it will respond only to the currentflow produced in the circuit by the high potential battery, and not tothat produced by the low potential battery. As the line relay 12 of thecalling line is energized, thus connecting the high potential battery tothe associated local conductor 253, the test relay 37 respends when thebrush '43 engages the terminal 47 of the calling line. The response ofthe relay 37 causes that relay to interrupt in its back contact thepreviously traced circuit by way of the left-hand armature and frontcontact of the relay 30, sequence switch contacts 216, and right-handwinding of relay 30, which circuit had been holding the relay 30 lockedup from the moment that the relay was first energized upon the re eiptof the call.- Relay 30 in releasing its armatures breaks its own lockingcircuit, and also breaks the previously-traced path, including sequenceswitch contacts 208, right-hand armature and front contact of the relay30, and sequence switch contact 207, over which current has been flowingto energize the updrive magnet 32 of the line finder. Therefore, theoperation of the relay 37 upon the finding of the calling line acts toefiect the instant deenerglzation of the up-drive magnet 32, and thus tostop the brushes upon the terminals of the calling line.

In order that the brushes may always be stopped in registration with theline terminals, the locln'ng circuit of the relay 30 has an alternativepath to ground by way of sequence switch contact 215 (2 to 4), conductor66, the C segment of the line finder commutator and the correspondingbrush to ground. The C segment of the commutator is so formed andrelated to its brush that the connection between the two is interruptedonly when the corresponding line brushes on the elevator rod areinengagement with corres onding sets of line terminals. The unloe of therelay 30, and the consequent stopping of the upward movement of theelevator rod, can therefore occur only when the line brushes are inproper relation to the terminals of the calling line. I When the relay30 is deenergized, as a result of finding the calling line, it alsocompletes a circuit that extends from battery through the motor magnetand contact 202 (3 to 4) of the finder sequence switch, righthand backcontact and armature of the relay 30, sequence switch contact 208 (2 to7), conductor 79, and M segment and corresponding brush of the cordselector CS to ground. The closure of this circuit moves the sequenceswitch out of position 4. When the finder sequence switch reachesposition 4%, it closes a path for the flow of current through thecut-off relay 11 of the calling line by way of resistance coil 64,sequence switch contact 212 (4% to 1211;), conductor 50, brush 42, lineterminal 46 and conductor 53.. The flow of current in this circuitoperates the cut-oif relay 11 to, disconnect the relay 12 from'thecircuit, and that relay in releasing its armatures disconnects the highpotential test battery from the local conductor 253 and disconnectsground from the common conductor 18. The disconnection til) of groundfrom conductor 18 occurs before the timing sequence switch 100 hascompleted its cycle of rotation and reconnected conductor 18 with role19.

The brushes of the line finder switch are now at rest in enga ement withthe termi nals of the calling line, the sequence switch 200 of findercircuit F is at position 6, the group starting circuit represented bythe conductors 57 and .58 and the associated relays 22, 23 and 33 hasbeen released and is in readiness to respond to another callm line, andthe sequence switch of another der circuit has been moved into position2, and thus brought into operative relation with the starting conductor29.

When the sequence switch of the finder circuit over which the call isbeing extended has reached position 6, the finder circuit is broughtinto operative relation with the operators selecting circuit. When thefinder sequence switch reaches position 6, it awaits the closing of acircuit, the completion of whichis deg-indent upon the condition of theother der circuits of the associated group. This circuit extends frombattery through the left-hand winding of the relay 30, contact 219 (6)of the appro- "priated circuit sequence switch contacts 219 (9 to 4:) ofthe sequence switches of the associated finder circuits preceding 1t 1nthe series, conductor 76, outer armature and back contact of relay 54,and right-hand back contact and armature of relay 61 to ground. A branchpath for the energizer tion of relay -.30 also exists at this time, thisbranch path extending from battery-through resistance 56, sequenceswitch contacts 217 (9, to 9), right-hand winding of relay 30, sequenceswltch contacts 220 (6) and (1 to i 13), and contact 219 (6) of theappropriate finder circuit sequence switch, from which point it extendsto ground at the righthand back contact and iarmature of the relay ()1over the path already traced. This circuit for the energization of relay30 is open either in the cam 219 of a preceding finder se uence switchin the series, or in contacts 0 the relay 54 or 61 as long as anysequence switch of the series is in positions 4 to 9. Th'at'is, it isopen from the time the line finder switch of any associated findercircuit finds a calling line until the cord finder switch of thatcircuit has moved far enough to trip the brushes corresponding with theselected operators position, as will be described. Not until this hasoccurred will the above-traced circuit of the awaiting finder circuit beclosed. When the circuit is closed, the relay 3O attracts its arinaturesand completes a circuit that extends from battery through the motormagnet and sequence switch contact 202 (6 to 7) of the sequence switch200, right-hand front contact and armature of relay 30, sequence switchcontact 208 (2 to 7), conductor 79 and segment M and corresponding brushof the cord selector commutator to grou d. The completion of thiscircuit moves finder se uence switch out of position 3.

hen the sequence switch 200 reaches position 6% it closes a circuit thatextends from battery by way of the winding of relay 55 (Fig. 3),conductor 71, sequence switch contact 218 (6:2 to 8), conductor 67,andsegment M and corresponding brush of the line finder commutator toground. The operation of the relay 55 applies ound to the conductors 81extending to al of the 0 erators positions. At each of the positlonswhere the operator is at her station and is in readiness to receive acall the associated relay 91 (Fig. 4) is inert, and the operatorstelephone sequence switch 300 is in its 1 position. Consequentl at eachof such positions, a circuit is c osed' that extends from battery,through the winding of the asso ciated relay 92, left-hand armature andback contact of relay 91, sequence switch contact 304: (1), conductor81, armature and front contact of relay 55 to ground. The relay 92 ofeach available osition therefore attracts its armature and c oses acircuit that extends from battery, throu h the front contact andarmature'oi the re ay 92 to the conductor 82, and thence to ground byway of the windings of the relays 77 corresponding to that operatorsposition at the various cord selector frames. X

When the finder sequence switch 200 reaches position 7, in whichposition it comes to rest, 1t closes a circuit that extends from batterythrough the winding of relay 54, left-hand back contact and armature ofrelay 61, conductor 73, finder sequence switch contact 218 (7 to 8),conductor 67, and segment M and corresponding brush of the line findercommutator to ground. Relay 54 attracts its armaturesand completes abranch of the circuit traced above, which branch extends from conductor73 1) way of the armature and back contact '0 the relay 63, frontcontact and inner armature of rela 54, armature and front contact ofrelay 77 (which relay is energized, as previously described, as a resultof the corres onding operators position being in readiness to receive acall), right-hand back contact and switch spring of relay 93 of thecorresponding group, winding of associated relay 94,

and resting contact of relay 93, ,con uctor 83, left-hand back contactand armature of relay 95 at the 0 operators osition to battery. Upon theclosure of t e above-traced -branch circuit, group relays 93 and 94 are.

energized in parallel withthe relay 54. Relay 93 in operatingdisconnects its own energizing winding and that of relay-94 from thepreviously traced path to battery by way of the left-liandback contactand armature of relay 95, and connects them in a path which extends tobattery by way of conductor 84 and the winding of the relay 95. Thiscauses the relay 95 a so to be energized and to interrupt in itsleft-hand armature and back contact the path by way of conductor 83 overwhich the relays 93 and 94 were initially energized. V

Relay 94 in operating closes a circuit from battery through the windingof the trip magnet 20 corresponding to the selected operators position,and to ground by way of the right-hand armature and front contact of therelay 94. This relay also closes a eucuit that extends from batterythrough the winding of the relay 63 and the left-hand armature andfront'contact of the relay 94 to ground. The relay 63 in operatingcloses a branch that extends from the conductor 7 3v (grounded by way ofcontact 218 (7 to 8) of the line finder sequence switch) through thearmature and front contact of relay 63,

conductor 72, sequence switch contacts 220 (7) and (1 to 13), andleft-hand winding of relay 30 to battery. A branch energizing path forrelay 30 also extends from conductor 72 by way of sequence switchcontact 220 (7), right-hand winding of relay 30, se quence switchcontacts 217 (2 to 9), and resistance 56 to battery. Relay 30 attractsits armatures and closes a circuit that extends from battery through themotor magnet and sequence switch contact 202 (6 to 7), front contact andright-hand armature of relay 30, sequence switch contact 208 (2 to 7),conductor 79, and segment M and corresponding brush of the cord selectorcommutator to ground. The closure of this circuit moves sequence switch200 out of position 7. Furthermore, relay 30 in operating is locked upover a circuit that extends from battery through resistance 56, sequenceswitch contacts 217 (2 to 9), right-hand winding of relay 30, sequenceswitch contacts 216 (7 to 9) and (2 to 9), front contact and left-handarmatureof relay 30 and armature and back contact of relay 37 to ground.When the sequence switch reaches position 8 it closes a circuit thatstarts the upward movement of the brush-carrying rod of the cordselector switch, this circuit extending from battery through theup-drive magnet34 of the cord finder, conductor 89,

sequence switch contact 207 (8 to 9), righthand front contact andarmature of relay 30, sequence switch contact 218 (8 to 9) conductor 67,commutator segment M of the line finder and corresponding brush toground. Y

At the outset of the upward movement of the cord finder brush rod, thetripping levers of the various sets of brushes are broughtsimultaneously into operative position with respect to the correspondingtripping yokes,

mosses energized. In the present instance, it is assumed that this isthe trip ma et 20 associated with the terminals of t e group ofconnecting cord circuits extending to the O operators position.Immediately after the set of brushes is tripped, the common operatorsselecting circuit is restored so as to be available for the use of othercord finder switches. This is effected through the medium of a circuitthat is completed by the grounding of the K segment of the cord findercommutator, this segment being so located as to be engaged by its brushimmediately after the tripping levers of the sets of brushes pass theassociated tripping yokes. The circuit referred to extends from batterythrough the winding of relay 61, conductor 74, sequence switch contact221 (72 to 8), conductor 80, cord finder commutator segment K and itscorresponding brush to ground. Relay 61 in operating opens, at itsleft-hand back contact, the previously-traced circuit by way ofconductor 73 which, up to this time, has been holding energized therelay 95 at the O operators position and the relays 93 and 94 forresponding to this position on the cord finder frame. The release of therelay 94 decnergizes the corresponding trip magnet 20 and the commonrelay 63. The deenergization of the relay 93 reestablishes, subject tothe release of relay 61, the control of other finder circuits over thebrush tripping mechanism of the associated cord finder frame. Relay 61,in operating, closes a locking circuit for itself by way of conductor73, sequence switch contact 218 (7 to 8), conductor 67 commutatorsegment M of the line finder and corresponding brush to ground. It alsocompletes a circuit that extends from battery through the motor magnetand contact 205 (8) of the sequence switch 200, conductor 7 5,right-hand front contact and armature of relay 61 to ground. The closureof this circuit moves sequence switch 200 out of position 8. In movingout of position 8, the sequence switch opens its contacts 218 (7 to 8),thus denergizing relay 61 and again extending conductor 73 to the relay54 and the conductors over which the operators selection is effected. Inclosing its right-hand back contact upon release, relay 61 also restoresthe continuity of con ductor 76 and makes it available for moving out ofposition 6 the sequence switch of some other finder circuit which may bewaiting for access to the operators selecting circuit.

After the cord selector switch CS passes the brush-tripping position, itcontinues its upward movement until the brushes are flow of current iscompleted from high potcntial battery 251 (see Fig. 4), through thewinding 0t common protective relay 197, armature and back contact ofthat 'relay, lower back contact and armature of relay 134, conductor128, right-hand armature and back contact of rela 119, lower backcontact and armature of relay 155, contact 404 (1) of the listening keysequence switch,

conductor 88, test terminal 118 and brush 114 of the cord selector,conductor 99, finder sequence switch contacts 206 (8 to 9) and thewinding of relay 37 to ground. Relay 37 thereupon attracts its armatureand opens the previously traced locking circuit that has been holdingrelay 30 energized. Relay 30, in releasing its armatures, opens at itsright-hand front contact and armature the 'ener zing circuit for theup-drive Ina net 34, t us stopping the brushes of the cor selectorswitch in engagement with the terminals 01 the selected connectingcircuit. lln

engaging its back contact, the right-hand armature of relay 30 closes anenergizing circuit for the motor magnet 01 the finder sequence switchwhich extends by wa of cam 202 (8 to 9), back contact and rlghthandarmature of relay 30, cam 218 (8 to 9),

a connecting cord sequence switch conductor, 67, and the M segment andcorresponding brush of the line-finder commutator to ground. The closureof this circuit moves sequence switch. 200 out of position 9, whereuponthe switch continues to move until it reaches position 14, where thetalking circuit is completed at cams 213 and 214.

An instant after the finder sequence switch leaves position 9, it closesa circuit that extends from battery through the windings of relays 151and 154-(see Fig. 5) in parallel, contact 505 (1), listening keysequence switch contact 405 (1), left-hand back contact and armature ofrelay 152, conductor 87, cord selector switch terminal 117 andcorresponding brush 113, conductor 98, and finder sequence 'switchcontacts217 (92 to 14) and (9% to 11) to ground. Relay 154 in operatingcloses a locking circuit for itself and relay 151 that extends by way ofits left-hand front contact and armature, connecting cord sequenceswitch contact 506 (1) and listening key sequence switch contact 406 (1to 6) to ground. Relay 154 also closes a circuit that extends frombattery through the motor magnet and cam 403 (1) of the listening keysequence switch, contacts 507 (17 to 8) and (1) of the connecting cordsequence switch and right-hand frontcontact and armature of relay 154 toground. The

closure of'this circuit causes the listening key sequence switch to moveout of position 1, and, in doing so, to open the test conductor 88 atsequence switch contact 404 (1), and also to open at sequence switchcontact 405 (1) the path over which the relays 151 and 154 were firstenergized.

Relay 151, associated with relay 154, in I operating closes a circuitthat extends from battery through the winding of relay 152 and outerfront contact and armature of re-' lay 151t0 ground. As a result relay152, prior to the moving of the listening key sequence switch out ofposition 1, has disconnected conductor 87 from connection with batteryby way of sequence switch contact 405 1) and the windings of relays 151and 154, and has connected it with an alternative path to battery by way01" the left-hand front contact of relay 152 and winding of relay 155.The relay 155 in operating closes at its upper front contact andarmsture a normal break in talking conductor 86, and at its lower backcontact and armature opens the path of test conductor 88. When thelistening key sequence switch reaches position 2, an additional path toound for holdin the relay 152 energized, 155 closed by wa 0 sequenceswitch contact 407 e energization of relay 151 at the instant the cordis seized also brings about the closure of a circuit that extends frombattery through the winding of the common relay 134, conductor 129,contact 502 (1) of the connecting cord sequence switch, and inner frontcontact and armature of relay 151 to ground. Relay 134 in o cratingopens at its lower armature and bac contact the circuit over which thepotential of the high voltage test battery 251 is applied to the testseized by a cord selector is withdrawn from the selected cord and alsofrom its associated cords at the instant of seizure, and is notreapplied to such of the cords as may be in condition to be selecteduntil the common relay 134 is deenergized. The deenergization of relay134 occurs when the relays 1'51 and 154 are released by the opening oftheir locking circuit at cam 406 when the listening key sequence switchmoves beyond position 6.

When the listening key sequence switch 400 is moved out of positlon 1,in the manner described above, it continues its movement until itreaches position 7. In position 7 the cams 408, 409, 410 and 411 of thelistening key sequence switch interrupt the talking strands of theconnecting circuit and include between their severed ends a loop thathas connection by way of conductors 135 and 136 with the operatorstelephone set 147. This puts the operator in communication with thecalling subscriber. At the same time the operator is informed of theidentity of the connecting cord over which the call is being extended bythe flashing of the lam 161 associated with that cord, the circuit orilluminating this lamp extending from battery through the reslst-ance163, lamp 161, calling cord sequence switch contact 514 (1 to- 2),listening key sequence switch contact 412 (12- to 18-1), and interrupter162 to ground.

As has previously been explained, when the sequence switch of anappropriated finder circuit reaches position 63-, it operates a tripmagnet on the cord selector frame that corresponds with a waitingoperators position, and at the same time operates the relay 95associated with the apparatus at that operators sition. When the relay95 at the operators position attracts its armatures, it closes a circuitwhich extends from battery through the winding of the relay 142,conductor 121, right-hand front contact and armature of relay 95, andright-hand front contact and armature of relay 125 to ground. Relay 142in operating closes a ocking circuit for itself that extends to groundby way of the inner front contact and armature of relay 142, operatorssequence switch contact 305 (16% to 15) and the right-hand front contactand armature of relay 125. The relay 142 in operating also closes acircuit that extends from battery through the motor magnet and contact303 (1 of the operators sequence switch, outer ront contact and armatureof relay 142, contact 306 (1 to 9) of the operators sequence switch andright-hand front contact and armature of relay 125 to ground. Theclosure of this circuit causes the operators sequence switch to move outof position 1 and to continue its movement until it comes to rest inposition 17. By causing the relay 95 to control the movement of theoperators sequence switch 300 out of position 1through the medium of thelocking relay 142, thls movement of the operators sequence switch ismade certain, even though there is only a momentary energization of therelay 95 in the selectlon of the operators position. As the lockingcircuit of the relay 142 is controlled in the contact 305 (16%} to 15)of the operators sequence switch, the locking circuit is broken and therelay 142 released the moment the sequence switch 300 passes beyondposition 15 in its movement to its resting position 17.

The left-hand windlng of the relay 91 is connected in parallel with thewinding of the relay 142; and as a result the instant relay 95 attractsits armature, the relay 91 opens, at its left-hand armature and backcontact, the path over which the relay 92 is energized when theoperators position is to be selected. This path is also opened atsequence switch contact 304 (1) an instant later when the operatorssequence switch is moved out of position 1 by the encrgization of thelocking relay 142. Thus the operators position is made inaccessible toother calls the instant it is selected, and is maintained inaccessibleuntil the operators sequence switch returns to position 1 and the relay91 is de'energized.

When the relay 95 operates upon the selection of the operators position,it closes a circuit that extends from battery by way of the left-handarmature and front contact of relay 95, conductor 120. and thencethrough two parallel paths, one of which extends through the winding ofthe relay 195 and the right-hand front contact and armature of relay 125to ground, and the other of which extends through the winding of therelay 145, upper back contact and armature of relay 153, operatorssequence switch contact 302 (18% to 15) and the right-hand front contactand armature of the relay 125 to ground. The relay 145 in operatingcloses at its front contact and armature an alternative path forsupplying current for main taining the energlzation of the relays 145and 195 after the relay 95 has released its armatures at the conclusionof the selecting operation. The relay 195 in operating effects certaincircuit changes the object of which will be described hereinafter. Therelay 145 in operating closes a circuit that extends from a source ofcall-tone current 143 through a condenser 144, right-hand front contactand armature of relay 145, and a winding of the operators induction coil146 to ground. Thus a call-tone is produced in the operators telephonereceiver the instant the relay 95 operates upon the selection of theposition. s the energizing circuit for the relay 145 which controls theapplication of the call-tone is controlled at the upper back contact andarmature of relay 153 and at the operators sequence switch contact 302(18"; to 15) the call-tone continues until the relay 153 is energized,or until the operators sequence switch, which is independently actuatedby the relay 95 at the instant of selection, as has been described,moves past position 15 in its movement from position 1 to position 17The energization of the relay 153 is effected by the closure of thecircuit that extends from battery through the winding of the relay 153,conductor 129, and upper front contact and armature of relay 134 toground. The relay 134, as has already been described, is energized bythe energization of the relay 151 at the moment the circuit by way ofconductor 87 is closed upon the seizure of the connecting cord of thecord selector switch. Thus the relay 153 is energized to dei nergize therelay 145 to withdraw the call-tone upon the seizure of the connectingcord at the selected operators position. As the continued energizationofthe relay 195 is under the warning of the selection of her 1positionby ciated with that cor position has been made inaccessible to otherhearing thecallrtone inher ,te phone receiver, and that a few momentslater she is apprised of the connecting cord that is to be used by theflashin of the lamp 161 assod. In the meanwhile the incoming calls bythe operation of the relay 91 and the movement of the operators sequenceswitch 300 out of position 1, and the operators telephone apgaratus hasbeen connected with the selecte connecting cord by the movement'of theconnecting cord sequence switch to position 7. The 0 erator now being incommunication with t e calling subscriber, inquires the number of theline that is wanted, and upon bein informed completes connection withthat me by insertlng the calling plug 170 into the correspondingspring-jack 14, first testing the line by touching'the tip of the plugto the sleeve of the spring-jack. 1f the line is busy, the potentialthat exists upon the sleeve of the spring-jack causes current to flow byway of the tip of the plug, the right-hand armature and back contact ofrelay 175, conductor 133, and winding of relay 184 to ground. Relay 184in o crating closes a circuit that extends from atterythrough theretardation coil 18,5 and the test winding of the operators inductioncoil 146 to ground. This causes a click in the operators telephonereceiver that tells her that the line is busy Assuming that the lineisfree for connection, the insertion of the plug 170 closes a circuitthat extends from battery through the coils of the relays 119 and 175 inseries, and thence by way of the registering sleeve contacts of the plug170 and spring-jaclr 14 to ground by way of the -winding of the cut-0drelay 11. The cut-ofi tip of the plug from the conductor 133 ex-'tending to the operators busy test relay 184, and connects it insteadwith the tip strand of the talking circuit. lRelay 175 also closes acircuit that extends from battery through the motor magnet and contact503 1) ofthe calling cord sequence switch, contact 413 (7) of thelistening key sequence switch, and left-hand front contact and armatureof relay 175 to ground. The closure of this circuit energizes the motormagnet and moves the call cord sequence switch out of position 1. Whenthe calling cord sequence switch reaches position 2 it comes to rest andcompletes a circuit that extends from battery switch, and right-hand bacthrough the motor ma et and contact 403 (7) of the listenin e sequenceswitch, contact 515. (2) of the callin cord sequence contact andarmature of relay 154 to ground. When the llstening key sequence switch400 moves out of position as the result of the closure of this clrcuit,it completes a circuit that extends from battery through the motormagnet and contact 504 (2) of the calling cord sequence switch, contact413 (8 to 15) of the llstening key sequence switch, and left-hand frontcontact and armature of relay 175 to ground, The closure of this circuitmoves the calling cord sequence switchout of position 2..

As the listening key sequenpe switch 400 movesbeyond position 8, itoperates its cams 408, 409, 410 and 411 to disconnect from theconnecting cord circuit the loop that extends to the o erators telephonecircuit by way of the con uctors 135, 136, 165 and 166 and con meets thetalking conductors 85 and 86 of the connecting cord circuit directlythrough to the left-hand windings of the'repeating coil 169.Furthermore, it interrupts the branch of the energizing circuit of thecord circuit holding relay 152 that had been completed to ground by wayof listening key sequence switch contact 407 (2 to 7) and leaves thecontinued energization of the holding relay dependent upon a path toground that extends by way of the right-hand front con- 1 tact andarmature of relay 152 and contact 508 (1 to 181) of the calling cordsequence switch.

After the calling cord sequence switch 500 is moved out of position 2 bythe movement of thelistening key sequence switch out of position 7 asdescribed above, it moves through its various stages (under the controlof the circuit which extends to ground by way of calling cord sequenceswitch contact 504 (4 to 13) and the right-hand back contact andarmature of relay 180) until it reaches position 12, at which point acircuit is closed that extends from battery through the winding of relayture and back contact of relay 178, armature and back contact of relay177 sequence 180, left-hand arma- 15), and sequence switch contact 516(3 to 13) to ground. The closure of this circuit energizes relay 180 andcauses it to open at its right-hand armature and back contact thecircuit by way of contact 504 (4 to 13) of the calling cord sequenceswitch which theretofore had maintained the energization of the motormagnet of that switch. As the cam 501 of the calling cord switch is cutso as to keep the energizing circuit of the motor magnet closed inposition 12 of the sequence switch, the switch continues to move untilit reaches position 13, where it comes to rest.

In position 13 of the calling cord sequence switch, ringing current isapplied to the connectingcord circuit to ring the bell at the calledsubscribers station. This is effected through the medium of a circuitwhich has two branches alternately closed in the rotation of thecommutator 182, one of the branches including the battery and the otherincluding a source of ringing current 181. From the commutator 182 thecircuit extends by way of sequence switch contact 517 (13), winding ofrelay 177. left-hand armature and front contact of relay 180, sequenceswitch contact 519 (13), ring contact of the calling plug 170, ringspring of the springjack 14, and thence over the corresponding side ofthe line to the called subscribers station and to ground by way of thesub-station condenser and bell. At the same time the other side of thecalled subscribers line is connected directly to ground by way ofsequence switch contact 518 (13). The closure of this circuit causes thebell at the sub-station to ring intermittently, and also by thediversion of a small part of the alternating current by way of thecondenser 183 and the winding of the repeating coil 169, causes theringing current to be heard by the calling subscriber. When the calledsubscriber in responding to the ringing of the bell takes his telephonereceiver from its hook, the resultant closure of the relatively lowresistance path across the limbs of the line causes an increase in thecurrent flow over the circuit just traced, and brings about theenergization of the relay 177. This relay is preferably so constructedand adjusted, in any well known way, as to make it insensitive to thealternating current flow that passes through it during the ringing ofthe hell but responsive to the current flow that takes place when thetelephone receiver is taken from its hook.

When the relay 177 operates, it opens the short circuit that normallyexists about the winding of the relay 178, which relay is included inthe path previously traced through the relay 180 and cams'507 and 516 ofthe calling cord sequence switch. The removal of the short circuitcauses relay 17 8 to attract its armatures. The opening ofthe left handarmature and back contact of the relay 178 prevents the reestablishmentof the short circuit about the relay 178 when the annature of relay 177-falls back after a momentary attraction. Engagement of the righthandarmature of relay 17 8, with its front contact closes a path frombattery including a resistance coil 17 9, which path is in parallel withthe, path from battery including-the relay 180. The resistance of thecoil 179 and the winding of the relay 180 are so proportioned that therelay 180 is shunted and releases its'armatures. The left-hand armatureof relay 180 in falling back opens the previously traced path over whichringing current was applied to the conncctin cor circuit. The right-handarmature o relay 180, in releasing and closing its back contact, closesa circuit that extends from battery through the motor magnet and contact504 (4 to 13) of the calling cord sequence switch. This causes thesequence switch to move out of position 13.

When the calling cord sequence switch leaves position 13, it moves toposition 16. In this position a circuit is completed that extends frombattery through the lower right-hand winding of the repeating coil 169,calling supervisory relay 187, sequence switch contact 519 (16 to 17),engagin rin contact surfaces of the calling lug 1 0 and called linespring-jack 14, tl fence to the called subscribers station over one limbof the line, through the sub-station apparatus and back over the otherlimb of the line to the engaging tip contact surfaces of the spring-jack14 and calling plug 170, righthand armature and front contact of rela175, sequence switch contact 518 (14 to 17) and upper right-hand windinof the repeating coil 169 to ground. The current flow in this circuitenergizes the calling supervisory relay 187 and causes it to close acircuit that extends from battery through the motor magnet and contact503 (16) of the calling cord sequence switch, and armature and frontcontact of relay 187 to ground. This moves the sequence switch out ofposition 16, whereu on it moves to position 17, which is the ta ingposition.

Up until this moment, the lamp 161, which, as described, was caused toflash when the call first came in, has been burning steadily as aringing lamp, the circuit for its illumination being to ground by way ofcontact 516 (3 to 16) of the calling cord sequence switch. When thesequence switch moves out of position 16, this circuit is interruptedand lamp 161 is extinguished. At the same time, a circuit is closed frombattery throughresistance coil 188, and thence by way of two branches,one of which extends through the calling supervisory lamp 189, left-handfront contact and armature of relay 119 and sequence switch contact 513(17) to ground, and the other of which extends by way of resistance coil190, sequence switch contacts 514 17 and armature and front contact ofrelay 187 to ground. The resistance in the latter branch is low, as aresult of which the calling supervisory lamp 189 is shunted out as longas tlcile calling supervisory relay 187 is energize When this stage hasbeen reached in the operation of the system, the talking circuit iscomplete between the calling subscriber and the called subscriber, thefinder circuit sequence switch 200 is inposition 14, the

called subscribers line.

calling cord sequence switch 500 is in position-i17, and thelistening-key sequence switch is in position 15, the listenin outposition. In this condition of the circuit,

the calling subscriber has control over the answering supervisory: lamp172 through the medium of the answering supervisory relay 171, and thecalled subscriber has control over the calling supervisory lamp 189through v'isory relay 187. As long as both subscribers havetheirtelephone receivers oil the switchhooks, these lamps are dark. Wheneither one of the-subscribers hangs up, 'the corresponding lamp islighted. When both lamps light at the same time, the operator knows thatthe conversation is at an end and takes down the connection.-

The operator disconnects by removing the calling plug 170 from the*rmg-jack of the his act permits relays 119 and 175 of the connectingcord circuit and the cut-off relay 11 of the calledsubscribers line tofall; back. The cut-off relay 11, in falling back, reconnects the linerelay 12 with the called 'subscribers line. Relay 119 in releasing itsright-hand armature reconnects the high potential battery I 251 with thetest conductor 88 of the cord is not entirel established, and the cordcir-- circuit. But the continuity of the connection of the testconductor 88 with battery cuit is there' ore not made selectable untilthe relay 155 has released itsa'rinatures and the listening sequenceswitch contact 404 has been closed by the return of the sequence switchto position-1. The relay 155 at its-lower armature opens the testconduetor 88 Whilethe talking circuit is established and thus reventsany. possible interference of the Eighpotential test battery 251 withthe set of class of service impulses common to the exchange. The otherarmature of the relay 119, in disenga ing its front cont-act, extingishes the cal ing supervisory lamp 189.

' Relay 175 in releasing completes a circuit that extends from batterythrough the winding of-relay 157, sequenceswitch contacts 512 (2 to 17),and left-hand back contact and armature of relay 175 to ground. Helay157 in operating closes a locking circuit for itself that extends by weof sequence switch contacts 512 (2 to 17), inner armature and frontcontact of rela .157, and sequence switch contact 510 2 to 17) toground: Relay 157 also closes a circuit that extends from batterythrough the motor magnet and contact 503 (2 to 17) of the calling cordsequence switch, outer front contact and armature of relay 157, andsequence switch contact 511 (2 to 18) to ground. The closure of thiscircuit moves the callin position 1 whereupon it-continues to rotate themedium of the calling supercord sequence switch 500 out of until itreaches and comes to rest in position 1, its normal position.

An instant after leaving position 17, the sequence switch 500 opens,atits contact 508 (1:1 to 18%), the path over which, up to this tune,the holding relay 152 has been main- .talned energized. The relay 152releases its armatures and brings about the return to normal of thefinder circuit and its assoclate'd apparatus in a. manner presently tobe described. When the calling cord so quence switch 500 reachesposition'l, it completes a circuit that extends from battery through themotor ma et and contact 403' (15) of the listening-file} sequenceswitchy contact'515 (1) of the ca lin cord sequence switch andr1ght-hand bac contact and --armature of, relay 154 to ground. Thismoves the listening-lie sequence switch 400 out of position 15 anpermits it to return to normal under the control of its cam 401. Whenthe holdingrelay 152 of the connectlng cord circuit becomes inert itbreaks at its left-hand armature and. front contact the circult by wayof conductor'87 of the connecting cord circuit, conductors 98 and 50 ofthe finder circuit and conductor 53 of the callingline, includingwindings of relays 155 of the cord circuit, 30. of the finder circuit,and '11 of the calling line; Consequently these three relays releasetheir armatures. Thecu-tofi' relay 11 of the callmg line. in releasingits armatures reconnects the line relay 12 with the line conductors 58and 39. Relay 30 of the finder cir- 100 cult 1n releasing closes acircuit fromlbattery through motor magnet and cam 202 (1 1) of thefinder sequence switch, lefthand back cont-act and armature of relay 30,and armature and back contact of relay 37 to ground. Thls moves thefinder sequence switch out of the talking position 14. When -the findersequence switch reaches position 15 a circuit is closed for theenergization of the relay 30 that includes in parallel branches bothwindings otthat relay. One branch of this circuit extends from batterythrough resistance 56, sequence switch coli- -tacts 217 (15 to 16) and(12 to 16), righthand winding of relay 30, sequence switch contacts 220(15) and (11 to 16) to conductor 67; the other branch extends frombattery, through the left-hand winding of relay- 30, and sequence switchcontacts 220 (15) and (11 to 16) to conductor 67; thence both branchesextend by way of conductor 07. and M segment and corresponding brush ofthe line-finder commutator to ground. He lay 30 in operating closes abranch path to ground for maintaining its energizatiomthis 12 Relay 30'in operating also closes a circuit that extends from battery, throughmotor magnet and contact 202 (15) of the finder sequenceswitchfiight-hand front contact 5 and armature of relay 30,sequenceswitch contact 218" (15), conductor-67, and" M segment andcorresponding brush of the line-' the path to ground by way of conductor67 and the M segment of the line-finder com-. mutator; the energizationof the relay being maintained in position 16 of the sequence switch bywe of the branch that includes its right-ban winding, com 216, left-handcontacts of relay 30, and resting contacts of relay 37. This circuitisheld closed and relay 30 is kept energized until the cord circuitthrough which the call was extended has returned to its normalcondition. When this occurs a circuit is closed that extends fromhigh-potential battery 251, through the winding and contacts of commonrelay 197 (see Fig. 4:), armature and back contact of relay 134,conductor 128, armature and back contact of relay 119, lower backcontact and armature of relay 155, sequence switch contacts 404' (1),closed when the cord circuit returns to normal, conductor 88,cordselector contact 118' and corresponding brush 114, conductor 99,sequence switch contact 208 (16), right-hand armature and front contactofrelay 30, sequence switch contacts 204 (9 to 17) and (16 and windingof relay 37 to ground. The closure of this ciru cuit energizes relay 37,which attracts its armature and opens the previously traced .holdingcircuit of the relay 30. Relay 30 in releasing its armatures closes acircuit't-hat extends from battery through the winding of down-drivemagnet 62 of the line-finder switch, conductor 60, sequence switchcontacts 22-3 (1-6 to 16%) and (16 to 7), lefthand back contact andarmature of relay 30, and armature and back contact of relay 37 toground (the energizing circuit of relay 37 having been interrupted atthe right-hand front contact and armatureof relay 30 when that relayreleased). As a result of the closure of this circuit, the brushes ofthe line- -finder switch are returned to normal. As the line-finderbrushes reach normal. a circuit is closed that extends from battcthrough the motor magnet and contact 20% (16) of the finder sequenceswitch, conductor 69, and Y segment and corresponding brush of theline-finder commutator to ground. When the finder sequence switchmovesto position 17, as a result of the closure of the amaze hand winding ofrelay 30, and also opens" above-traced circuit, a cu'citit is completed'that extends from battery through the winding of the down-drive magnet35 of the cord selector, conductor 90, finder sequence switch contact218 (17), conductor 67, and M segment and corresponding brush of theline-finder commutator to ground. The closure of this circuit returnsthe cord selector switch to normal; and as the brushes reach normal, acircuit is closed that extends from battery through the motor magnetwinding and contact 205 (17) of the finder sequence switch, conductor31, and Y segment and corresponding brush of the cord selectorcommutator to ground. The closure of this circuit causes the findersequence switch 200 to return to its normal position. As hashereinbefore been explained, the operators position is selectable by anincomin call only when the'operators. sequence SWltCh 300 is standing inposition 1. When the relay 95 is ener 'zed upon the selection of theposition, t e operators sequence switch is moved to position 17 in theman ner hereinbefore explained, and thereafter remains in that ositionuntil it is returned to position 1. T e circuit for returning theoperators sequence switch from position 17 to position 1 extends frombattery through the motor magnet and contact 303 (17) of theoperatorssequence switch,and is completed to ground by way of the upper armatureand front contact of the relay 192 of the associated positionwhen thatrelay is operated. The energizing circuit of each of the relays 192 atthe various operators positions extends from battery through the windingand lower switch spring and resting contact of that relay, theright-hand urmature and back contact of the associated relay 91, andcontact 307 (15 to 18) of the associated operators sequence switch to aconductor 140 which is common to the energiz ing circuits of all of thepositions, this conductor 140 extending to ground by way of 110. theseries of operators sequence switch contacts 308 ('2 to 18) one of whichis associated with the sequence switch of each operators position.Consequently when the sequence switches 300 of the entire series ofoperators positions have been advanced to position 2 or beyond by theselection of these positions by incoming calls, or otherwise, as will beexplained, the path to ground by way of the conductor 139 is closed, allof the relays 192 the paths of which are completed to the conductor 140are energized, and the operators sequence switches at such positions aremoved out of position 17 and come to rest in position 1. Thus thesepositions are again rendered available for receiving incoming calls. Inorder to insure the closure of the energizing circuit of relay 192 for asuliiciently long interval to effect the movement of the associatedSequence'switch, the relay 13o in operating closes a locking circuit foritself to ground by way of operatorssequence switch contact 310 (15 to8), this locking path being opened to release the rela when the sequenceswitch moves beyon position 18.

It may at times be necessary for the operator to supervise or listen inon an estabhshed connection. In order that the operator may bring hertelephone apparatus into connection with a clrcuit upon which connectionhas been established, it is necessary that the associated listening keysequence switch 400 be moved from' its listening-out position 15 toitslistening-in position 7. This is accomplished by pressing theassociated listening-in key 191, which closes a circuit that extendsfrom battery through the motor magnet and contact 402 (15) of thelistening key sequence switch, right-hand contact and switch spring oflistening-in key 191,

conductor 130, ri ht-hand armature andback contact of re ay 195,right-hand back contact and armature of relay 95, and righthand frontcontact and armature of relay 125 to ground. As a result of the closureof this circuit the listening key sequence switch moves out of position15. Upon reaching position 1, it is moved through this position by acircuit that extends from battery through the motor ma net and contact402 (1) of the listening key sequence switch, and contacts 511 (2 to 18)of the calling cord sequence switch to ground. Consequently thelistening key sequence switch continues to move until it reachesposition 7, in which position the operators telephone apparatus is againconnected with the circuit through the medium of the listening keysequence switch, cams 408, 409, 410, 411. Having supervised theconnection, the operator may disconnect her telephone apparatus from thecircuit by pressing the listeningout key 186, which is common to all ofthe connecting circuits of her position. This closes-a circuit thatextends from battery through the motor magnet and contact 403 (7) of thelistening key sequence switch, and. contacts of the master listening-outkey 186 to ground. As a result the listening key seqnence switch iscaused to move out of posi-- tion 7 and again come to rest in position15. Or the operator may listen out on one connection by listening in onanother. This is effected through the multiple connections which existbetween the contacts 402 (7) and the contacts 406 (2 to 6) of all of thelistening key sequence switches. When any listening key sequence switchis standing in position 7, the movement of the listening key sequenceswitch of any other connecting circuit through positions 2 to 6 afi'ordsan energizing path to ground for the motor magnet of the listening keysequence switch that is standing in position 7.

When the operator presses a listening-in ke' 191 to supervise theconnection establis ied on the corresponding circuit, it is desirablethat in doing so that she shall render her position unselectable by anincoming call if her sequence switch 300 is standing in its waitingposition 1; and also, if her sequence switchis standing in position 17,that she shall prevent it from being returned to position 1 by relay192, as described, in which-position the operators position would againbe selectable. To accomplish this, the depression of the listening-in ey191 completes a circuit that extends from battery through the lefthandwinding" of relay 91, left-hand armatureand back contact of relay 195,conductor 138, listenin key sequence switch contact 414 (9 to 16? andleft-hand contact and switch spring of the listening-in key 191 toconductor 130, from which point the path to ground is as has alreadybeen traced. If the operators sequence switch is standing in position 1,the

relay 91, in attracting its armatures as a result of the closure of thiscircuit, opens at its left-hand armature and backcontact the energizingcircuit for relay 92, which relay, as has already been explained,controls the selection of the position. If the op erators sequenceswitch 300 is standing in position 17 when the listening-in key 191 ispressed, the energization of the relay 91 opens, at the right-handarmature and back contact of that relay, the path over which the relay192 receives its energizin current from conductor 140 when all of tieoperators sequence switches 300 of this group of operators have'beenmoved out of position 1 and-are standing in position 17, or in someposition between 2 and 18. Therefore, if the operator presses herlistening-in key 191 an instant before the last of the series- "ofsequence switch contacts 308 (2- to 18') is closed, her sequenceswitch300 will be prevented from being restored to position 1. where it wouldrender the position immediately accessible to an incoming call which,

'when it seized a connecting cord, would automatically disconnect theoperators telephone from the cord circuit she was attempting tosupervise.

In moving from the listening-out position 15 to the listening-inposition 7 as a result

